Tuesday, May 07, 2013

Qt 5 in Debian and Ubuntu, patches upstreaming

Packages

I quite like the current status of Qt 5 in Debian and Ubuntu (the links are to the qtbase packages, there are ca. 15 other modules as well). Despite Qt 5 being bleeding edge and Ubuntu having had the need to use it before even the first stable release came out in December, the co-operation with Debian has gone well. Debian is now having the first Qt 5 uploads done to experimental and later on to unstable. My work contributed to pkg-kde git on the modules has been welcomed, and even though more work has been done there by others, there haven't been drastic changes that would cause too big transition problems on the Ubuntu side. It has of course helped to ask others what they want, like the whole usage of qtchooser. Now with Qt 5.0.2 I've been able to mostly re-sync all newer changes / fixes to my packaging from Debian to Ubuntu and vice versa.

There will remain some delta, as pkg-kde plans to ask for a complete transition to qtchooser so that all Qt using packages would declare the Qt version either by QT_SELECT environment variable (preferable) or a package dependency (qt5-default or qt4-default). As a temporary change related to that, Debian will have a debhelper modification that defaults QT_SELECT to qt4 for the duration of the transition. Meanwhile, Ubuntu already shipped the 13.04 release with Qt 5, and a shortcut was taken there instead to prevent any Qt 4 package breakage. However, after the transition period in Debian is over, that small delta can again be removed.

I will also need to continue pushing any useful packaging I do to Debian. I pushed qtimageformats and qtdoc last week, but I know I'm still behind with some "possibly interesting" git snapshot modules like qtsensors and qtpim.

Patches

More delta exists in the form of multiple patches related to the recent Ubuntu Touch efforts. I do not think they are of immediate interest to Debian – let's start packaging Qt 5 apps to Debian first. However, about all of those patches have already been upstreamed to be part of Qt 5.1 or Qt 5.2, or will be later on. Some already were for 5.0.2.

A couple of months ago Ubuntu did have some patches hanging around with no clear author information. This was a result of the heated preparation for the Ubuntu Touch launches, and the fact that patches flew (too) quickly in place into various PPA:s. I started hunting down the authors, and the situation turned out to be better than I thought. About half of the patches were already upstreamed, and work on properly upstreaming the other ones was swiftly started after my initial contact. Proper DEP3 fields do help understanding the overall situation. There are now 10 Canonical individuals in the upstream group of contributors, and in the last week's sprint it turned out more people will be joining them to upstream their future patches.

Nowadays about all the requests I get for including patches from developers are stuff that was already upstreamed, like the XEmbed support in qtbase. This is how it should be.

One big patch still being Ubuntu only is the Unity appmenu support. There was a temporary solution for 13.04 that forward-ported the Qt 4 way of doing it. This will be however removed from the first 13.10 ('saucy') upload, as it's not upstreamable (the old way of supporting Unity appmenus was deliberately dropped from Qt 5). A re-implementation via QPA plugin support is on its way, but it may be that the development version users will be without appmenu support for some duration. Another big patch is related to qtwebkit's device pixel ratio, which will need to be fixed. Apart from these two areas of work that need to be followed through, patches situation is quite nice as mentioned.

Conclusion

Free software will do world domination, and I'm happy to be part of it.